We were cleared to FL220 and cleared direct to mco when able (previously assigned a heading). I stayed on heading a little while (2 or 3 mins) to avoid some buildups in the direction of mco. I told first officer to notify ATC that I wanted to stay on this heading a little while longer. When he finished we were going through 20400 ft. The controller immediately came back and asked what altitude we were at. At the same time we got a TA followed by an RA on TCASII, I spotted the traffic ( he was at FL210) and got right back down to FL200. Apparently the controller thought he cleared us to FL200 but we were cleared to FL220 and this set up the conflict. He was very busy at the time. Both the controller and the TCASII system spotted the conflict before it became a near miss!

Narrative: WE WERE CLRED TO FL220 AND CLRED DIRECT TO MCO WHEN ABLE (PREVIOUSLY ASSIGNED A HDG). I STAYED ON HDG A LITTLE WHILE (2 OR 3 MINS) TO AVOID SOME BUILDUPS IN THE DIRECTION OF MCO. I TOLD FO TO NOTIFY ATC THAT I WANTED TO STAY ON THIS HDG A LITTLE WHILE LONGER. WHEN HE FINISHED WE WERE GOING THROUGH 20400 FT. THE CTLR IMMEDIATELY CAME BACK AND ASKED WHAT ALT WE WERE AT. AT THE SAME TIME WE GOT A TA FOLLOWED BY AN RA ON TCASII, I SPOTTED THE TFC ( HE WAS AT FL210) AND GOT RIGHT BACK DOWN TO FL200. APPARENTLY THE CTLR THOUGHT HE CLRED US TO FL200 BUT WE WERE CLRED TO FL220 AND THIS SET UP THE CONFLICT. HE WAS VERY BUSY AT THE TIME. BOTH THE CTLR AND THE TCASII SYS SPOTTED THE CONFLICT BEFORE IT BECAME A NEAR MISS!

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.